The present invention relates to a method of forming chemical mechanical polishing pads. More particularly, the present invention relates to a method of forming chemical mechanical polishing pads using surfactants.
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting and dielectric materials are deposited onto and removed from a surface of a semiconductor wafer. Thin layers of conducting, semiconducting and dielectric materials may be deposited using a number of deposition techniques. Common deposition techniques in modern wafer processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD) and electrochemical plating, among others. Common removal techniques include wet and dry isotropic and anisotropic etching, among others.
As layers of materials are sequentially deposited and removed, the uppermost surface of the wafer becomes non-planar. Because subsequent semiconductor processing (e.g., metallization) requires the wafer to have a flat surface, the wafer needs to be planarized. Planarization is useful for removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches and contaminated layers or materials.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize or polish work pieces such as semiconductor wafers. In conventional CMP, a wafer carrier, or polishing head, is mounted on a carrier assembly. The polishing head holds the wafer and positions the wafer in contact with a polishing layer of a polishing pad that is mounted on a table or platen within a CMP apparatus. The carrier assembly provides a controllable pressure between the wafer and polishing pad. Simultaneously, a polishing medium (e.g., slurry) is dispensed onto the polishing pad and is drawn into the gap between the wafer and polishing layer. To effect polishing, the polishing pad and wafer typically rotate relative to one another. As the polishing pad rotates beneath the wafer, the wafer sweeps out a typically annular polishing track, or polishing region, wherein the wafer's surface directly confronts the polishing layer. The wafer surface is polished and made planar by chemical and mechanical action of the polishing layer and polishing medium on the surface.
Hirose et al. disclose a method of making polishing layers in U.S. Pat. No. 8,314,029. Specifically, Hirose et al. disclose a method for manufacturing a polishing pad containing substantially spherical cells and having high thickness accuracy, which includes preparing a cell dispersed urethane composition by a mechanical foaming method; continuously discharging the cell dispersed urethane composition from a single discharge port to a substantially central portion in the width direction of a face material A, while feeding the face material A; laminating a face material B on the cell dispersed urethane composition; then uniformly adjusting the thickness of the cell dispersed urethane composition by thickness adjusting means; curing the cell dispersed urethane composition with the thickness adjusted in the preceding step without applying any additional load to the composition so that a polishing sheet including a polyurethane foam is formed; and cutting the polishing sheet. This process can have difficulty in controlling pore size and pore size distribution. Also, the complicated process can create fouling issues that can decrease manufacturing efficacy.
Notwithstanding, there is a continuing need for improved methods of manufacturing polishing layers for chemical mechanical polishing pads having better control of pore size and pore size distribution. Particularly for methods that reduce the total number of process steps required and improve quality of the completed polishing pad. Hence, what is needed is an improved method of providing a polishing layer for a chemical mechanical polishing pad, having enhanced polishing performance and manufacturability.